It is unfortunately fairly common for companies to overstate the restrictions of the AGPL. But as the AGPL states, additional restrictions can be removed.
This answer is primarily based on the GPLv3 CommunityServer license you linked. But aside from the GPLv3 vs AGPLv3 point, the analysis is identical for the AGPLv3-covered DocumentServer which contains the same additional terms.
The actual license terms
Here, it is important to pay attention: The code in their CommunityServer GitHub repository and their Debian package currently uses the GPLv3 (Internet Archive snapshot) without any additional terms in the README or license, but with the following additional terms in the source files:
In accordance with Section 7(a) of the GNU GPL its Section 15 shall be amended to the effect that Ascensio System SIA expressly excludes the warranty of non-infringement of any third-party rights.
The interactive user interfaces in modified source and object code versions of ONLYOFFICE must display Appropriate Legal Notices, as required under Section 5 of the GNU GPL version 3.
Pursuant to Section 7 § 3(b) of the GNU GPL you must retain the original ONLYOFFICE logo which contains relevant author attributions when distributing the software. If the display of the logo in its graphic form is not reasonably feasible for technical reasons, you must include the words "Powered by ONLYOFFICE" in every copy of the program you distribute.
Pursuant to Section 7 § 3(e) we decline to grant you any rights under trademark law for use of our trademarks.
Of course, they can license downloads via their website or binaries etc under the AGPLv3 instead. The software would also be effectively covered by AGPLv3 when combined with the AGPLv3 components of their offering, e.g. the DocumentServer.
Analysis of additional terms
The additional terms consist of three parts:
- A warranty disclaimer per GPLv3 section 7(a). It is correct and effective, though superfluous.
- A requirement for retaining certain notices and attributions per GPLv3 section 7(b). This is unclear and discussed further below.
- A refusal to license their trademarks per GPLv3 section 7(e). It is correct and effective, but is imprecise and seems contradictory with the requirement to use their logo.
An additional term per section 7(b) requiring “preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works” is allowed, but Ascensio's term is overly broad and therefore partially defective.
Ascensio wants you to display:
- the original ONLYOFFICE logo in its graphic form, on the basis that it contains relevant author attributions
- if displaying graphics is not possible, the words "Powered by ONLYOFFICE"
The (A)GPLv3 defines Appropriate Legal Notices thusly:
An interactive user interface displays “Appropriate Legal Notices” to the extent that it includes a convenient and prominently visible feature that (1) displays an appropriate copyright notice, and (2) tells the user that there is no warranty for the work (except to the extent that warranties are provided), that licensees may convey the work under this License, and how to view a copy of this License. If the interface presents a list of user commands or options, such as a menu, a prominent item in the list meets this criterion.
This allows the following contents of an Appropriate Legal Notice:
- appropriate copyright notices
- warranty exclusions
- information to the user about their right to convey the software under this license
- how to view a copy of this license
Nothing from the items required by Ascensio matches the definition of an Appropriate Legal Notice. E.g. the logo contains a product name, but no copyright notices.
Similarly, those items fail to be “reasonable legal notices”.
However, the logo and the “Powered by” phrase could count as “author attributions”. But such author attributions do not have to be a “convenient and prominently visible feature” of the user interface.
By talking about AGPL but using GPL, and by introducing mild to serious defects into all their section 7 additional terms, Ascensio has demonstrated a serious lack of understanding about their licensing.
- Due to their potentially defective licensing approach, end users of Onlyoffice-derived software may not be eligible to receive the source code.
Furthermore, by asking for derivatives (potentially created by competitors) to use their logo, they are creating a contradiction with the refusal to license their trademarks and are at risk of diluting it.
Contrary to their statements, removing their logo etc. is largely OK. It does not have to be used in the branding of a derivative work, but must be shown as part of the attributions for the original work. In any location where you mention your copyright in the software and mention the license, you should also mention Ascensio's copyright and show the logo.