I don't know if there is a big difference in getting an SSL certificate or a Codesigning certificate. LWJGL has the latter, and I assume that's what you really want?
The primary and most important issue with Open Source, particularly online collaborative project such as jME and LWJGL, is that it MUST be a *legal* entity. This is one of the reasons why LWJGL for several years was signed by Oddlabs. With Elias no longer active in the project, that was basically no longer an option.
So for LWJGL, I registered whats called an 'Frivillig Forening', in Denmark. This type is basically the closest thing you get to a non-profit, ownerless organization. You may have a similar thing.
Once you have that, let me know - I may be able to hook you up with a free 2 year code signing certificate from thawte.