Sealing a cork tile floor?
Congratulations on the cork.  I put cork in my master bathroom a few years ago and it was the best floor I've ever had - warm in the morning and soft under bare feet.  I liked it so much I put cork in our kitchen too.

My feeling is that you don't need to seal it.  I didn't see any lifting or swelling on our floor over three years.  We're not especially fastidious people either - we basically just swiped puddles with a towel when we saw them.

Any sealant you put on that is capable of sealing the joints will be a film finish.  My gut says the subtle expansion and contraction of the cork along with the flex of the floor will crack a film finish like that in pretty short order, defeating the purpose.

One thing you could try if you're nervous is some clear wax.  Test it under a cabinet or something to see if you can force a tiny bit into the seam and still thoroughly remove it from the surface.  Also satisfy yourself that the solvent in wax doesn't damage the finish of the cork tiles. If it works ok, it might slow down penetration of water into the seams while still remaining flexible.