A open software license generally outlines what conditions that a fellow software developer must follow in respect to the original project, be it someone who is plain out of the blue looking at it, and debating whether to do something to it, or whether it is a full-out fork or derivative. Basically, they just dictate what you can do. For example, the WTFPL makes absolutely clear it's single clause:
0.You just DO WHAT THE FUCK YOU WANT TO.
However, many projects that are distributed to the general public are normally accompanied with the End User License Agreement, or EULA. According to Avangate: (emphasis mine)
The EULA (End User License Agreement) is, as its name shows it, a contract between the software developer and a potential user. By means of this contract it is established that the developer of the software is its de facto owner, and that a copy of the respective software bought from a vendor (or downloaded from the Internet) only licenses it to a user...
The end user is only allowed to use it as long as certain terms are respected, and is also prohibited from any alterations or uses of the software without the specific consent of its rightful owner, the software company/developer.
Does another developer count as a potential user? To me, it looks like yes: They are using the software, just in a different way from someone within the general public: they are using the code, but not necessarily the intended functionality, but they are still "using" it.
Aside from what a "potential user" is really defined as, it sounds like an End User License Agreement is a license. If the developers behind a fork/derivative are "users" of the original project, could they be subject to the terms and conditions of the End User License Agreement? Is an EULA the same thing as a license? Where is it ever appropriate to use an EULA in a project?