Perhaps you could clarify what you mean by "the next step". Is there a possibility of more developers arriving on the scene? Or are you just (rightfully) paranoid about what could go wrong even with 2 people.

I was surprised when I didn't see CVS mentioned. Then I saw it in the last line. I'm rooting for CVS because of the sheer power involved. Being able to note differences between versions (ie: between multiple edits), as well as being able to restore previous versions should something go whacko. It's like having a mini-backup of the project at all times (though a proper backup is still required of course). Add the authentication schemes and the rest of the packaged goodies, and CVS just seems to glow.

Just curious: are some of these files interlinked with other files in the project? Do you need to be able to work on 4 separate files all at once without intervention from another developer who wants to make other changes to one of the files?

If the above content is missing any vital points or you feel that any of the information is misleading, incorrect or irrelevant, please feel free to downvote the post. At the same time, please reply to this node or /msg me to inform me as to what is wrong with the post, so that I may update the node to the best of my ability.