I'm not one to be recommending other engines/frameworks on LOVE's forum, but...if your main goal is to make a 2D MMO and not to necessarily learn LOVE, it may be beneficial to learn and work with a 2D MMO engine (not one of those "MMO creator" thingys - an engine). I've heard a lot of good stuff about Eclipse (
http://www.touchofdeathforums.com/eclipse/ ), and some tinkering around with it a few years ago proved it easy to use and work with. It has its own scripting language, and it's also open source so you can delve into the source code (C++, I believe...though actually it may be Java) if the need arises. It's got quite a large community around it too (though note that the engine has just recently been completely rewritten, so some older tutorials and such may not be worth much).
If, on the other hand, the goal is to build the majority of your engine from the ground up (i.e. only using libraries), then LOVE would probably be a really good choice. It just depends on your focus: rapid development or the joy (or potentially pain) of writing everything yourself from very little. The latter option, among other advantages, also gives you the opportunity to keep things much cleaner since you'll only put in what you need. Then there's, of course, the experience and knowledge gained from doing everything yourself.
Either way, an MMO is a big project. While something like Eclipse can make it a lot easier (particularly since all of the server and network code, including user accounts, admins, chatting, banning, updates, etc..., is all taken care of), it's still a pretty large task. I really wouldn't recommend that you start off in the direction, particularly if you are starting with a more generic 2D framework like LOVE. Anyone who's floated around game dev forums long enough has seen countless people try to start with an MMO, only to get discouraged and quit game design/programming all together. If you absolutely must start with something like this, then I'd suggest starting with a simple, small multiplayer (NOT massively multiplayer) game in the style that you want. Something meant to have four or five players playing at once. That way you don't have to worry about master servers, persistence, admins, or a lot of the other more complicated stuff that comes with a MM game.
EDIT: Sorry, I misunderstood - I was thinking that you were a newcomer to game dev (though it appears that you may be a newcomer to programming?). Most of what I wrote still applies though
If you've already made a SP version of your game, then I still suggest that you try making a simple multiplayer version of it first, especially if you will be using a more generic framework like LOVE. Trying to make a full MMO (simple or not) during your first stab into 1. programming, and 2. a framework/engine will most likely end in frustration. Start small.