Seems kind of excessive, but an interesting start. I have a few suggestions though.

Don't make the RegExp methods static class methods, then you can manage a server connection per-instance, which might help performance issues. Chances are if you are going to use this, you are going to use it for larger reg-exp problems and not just simple ones, so it seems to me there is a good chance you will run multiple reg-exps to the server.

Even though it could be dangerous, I would allow a full reg-ex to be sent to the server. Like this:

boolean result = myRegExpInstance.match('/(.*?)somethings/i');
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Then you don't need to worry about all the possible modifiers and how to handle them in your protocol.

I would also suggest then parsing the reg-exp a little, you could could the number of () you have and then make those matches available. You should also test for any embedded perl code, and disallow it. Obviously this can get really messy, but I think it's complexity can easily be managed over time (only implement a little at a time, as the need arises maybe).

Cool idea :)