The Law
You might compare it to making a movie of a book, or a translation if you like. Now the law says I can do that, but will need approval from the owner of the original to be able to publish it. They even may have a right to ask me for a fair retribution, or they just simply can forbid me to publish it.
If I do publish it without concent I would be infringing their copyrights since it is based upon their work. My additions and changes to this work are still copyrighted by itself, so they cannot claim it, but only the changes I made don't make up the complete work. Probably if I did publish it now, I can expect another summon to take it down in no-time. Maybe if I published it outside the Netherlands Brein will keep out of it, but it still wouldn't be fully legal and other 'software police foundations' may come after me. I could also spread out full copies, but all that would take away the reason for making this game: a technical demonstration of the possibilities of DHTML.
I don't wish to go down that road, or even risk being sued over this, so my only option is to get permission from the legal owner of Lemmings™. Now that's where you may be able to help me...
First of all there still seems to be some misunderstanding about who actually is the legal owner of Lemmings™. In my opinion the most likely candidate is Take 2 Games since their affiliate Talonsoft published Lemmings™ Revolution in the year 2000. Another possible candidate is Sony Computer Entertainment since they took over Psygnosis and also published a Playstation version of Lemmings.
If someone, without any doubt, could tell me who actually owns the rights to Lemmings™ than the first most important item in my quest would be solved.