Want to form independent research group outside university, while working?
You need to find people that will share your research interests. To get them interested, you first have to offer something. Let's talk software prototypes.


Publish your (possibly beta version, possibly not-very-product-quality) software prototype so that other people could download it.
Publish documentation so that those people could use it after they download it.
Arrange a mailing list / forum so that people could suggest improvements after they use your software.
Possibly, make it open-source so that people could make the said improvements themselves.


Having some prototype to touch, explore and work on will, based on my experience, bond your newborn community more than just discussions. It is important to have something tangible before you start scouting for people.

Also, it may be easier to find people for your project offline. Talk to people of your age and interests in your local university (even if you are not affiliated), in computer science conferences and enthusiasts meetings (there might be some in your area).

The advice above is based on my personal experience of involving people into collaboration and inspired by this article.