I got excited when I saw that added to the terms of service. Rights of First Refusal can be a good tool for artists trying to get published. I actually have two written into my contract with my current publisher.
The first one I added, saying that I get the right to decide if I want to work on another book if they decide to continue the series I'm working on before they'd be able to ask another artist/writer. The second is more like what we've got here, which is that my publisher has the right to decide if they'd like to make an offer to publish whatever book I write next.
Tapastic is doing something similar, just with a project you're already working on and posting on their site. This is cool for two reasons:
1. AUTOMATIC EYES ON YOUR WORK. If you're going to start pitching your comic to publishers, Tapastic is asking to be the first to see it and make an offer. It's not guaranteed that they'll make an offer, but at least they'll take a look which is more than some publishers might do if you're sending your comic to them unsolicited.
2. Healthy competition. If you get an offer from another publisher, you can contact Tapastic and let them know, and once again they might make an offer. If they do, this is a bargaining chip for your contract negotiation! You get to tell the interested publisher that there's another "interested party who has made an offer" and give yourself better leverage in negotiating a contract with whoever ends up offering you the best terms, Tapas or the other guy.
Chances are another publisher or host wouldn't want you to also have your comic up on Tapas for free if they're paying you for it, so if you're comic is popular on Tapas they might offer you a good deal to keep it on their site. Or they might offer you better terms when it comes to copyright or something, since they're into creator owned comics. At the very least it would give you things to consider. It's not like a little mermaid thing where you have to agree to whatever terms given to you and Tapas owns your voice now, it's just giving Tapas the chance to negotiate with you and see if you can reach an agreement that works for everyone.
Also, I wouldn't worry too much about the 30 days thing. If you tell your interested party that you have another party with rights of first refusal and you have to contact them (or something even vaguer, you don't HAVE to give them the full dealio) and they freak out and give you a week to make up your mind... that's probably a red flag. In editorial, there are a lot of fast and loose contracts flying around, but in publishing a contract can take a lot of time to get ironed out and professionals know that. There are plenty of predatory publishers out there so you should always take the time to really look over any contract and get a few other sets of eyes on it as well! Especially if this is a comic that you've been putting your heart into for a long time, you're going to want to think long and hard about how much it's worth to you and what things you're willing to be flexible about. I don't currently have an agent, but I was lucky enough to have a few agents offer to look over my contract for free and help me figure out things I should ask for in my terms.