Hello Will mische
As far as the stealing goes nothing can be done but if your code is too costly or very important then you can use lawyer but for that you must have something like acceptance of terms and conditions.
If you dont have that one thing you can do for sure is just give them a threat that you can do the legal work it may help but not will help.
Also you can request the hosting co. that the code belongs to you and your subscriber does not own that code and he can take legal action against them also as they are hosting the copyrighted code without prior written permission. This is also just a trial as they will support there customer and not you but this are some of steps that can be taken but there is nothing else you can do.