Beware of projects which claim to be open source but don't have a standard license approved by the FSF or approved by the OSI.
- Some people misunderstand what "Open Source" actually means. It is a very common misconception that simply allowing people to look at the source makes it open source. It doesn't - that's called "Source Available". To be really open source, a project must be licensed under a license which fulfills the open source definition. A very popular license clause some people try but which prevents a project from being open is a non-commercial clause. It violates the right of "No Discrimination Against Fields of Endeavor, Persons or Groups". It's far better to just use an existing license like the GPL which theoretically allows commercial use but practically has various conditions which make most common business models these people are usually afraid of completely infeasible.
- Writing licenses is hard. Licenses are legal documents. When you are not a trained lawyer and try to write one, it will likely not say what you want it to say or include clauses which are simply invalid or meaningless. So even when the author understood the definition of open source and wants his project to follow this philosophy, their homebrewed license might still be proprietary without them realizing.
So how to deal with such licenses?
When the license is short, you could try to evaluate for yourself if it fulfills the open source definition or the definition of free software. But when the license is longer or hard to understand, chances are that as a legal layman you will be out of your league. The best advise would be to ask a lawyer, but unless you have commercial interest in the software, you likely don't want to afford one.
You could also try to convince the author to switch to an approved open source license. There are so many licenses available that they will likely find one which says what they want (as long as what they want is actually open source). When they still do not want to abandon their own license, you might be able to convince them to at least dual-license the software under both their homebrewed license and a proper open-source license so that people can choose which one to use.
When they also refuse to do that, you might still decide to use it and even contribute to it, but you must be aware that the software might be gratis but not free and that when you contribute, you might be performing gratis work for a proprietary product. What you should do under no circumstances is merge the code into another project. That way you plant a legal landmine in the other project which might not just blow up on you but also on any downstream users.
