The trademark issue is very low on my worry list...
I suppose it would be up to the purchaser to make sure that what they intend to do with the domain doesnt infringe upon any trademarks... in the searching I've done.. there's 11 registered live federal trademarks using the word "Lightwave" none of which are in the same Goods & Services or Class categories as what I'd envision the user of the domain would use it for.
FWIW, the trademark to the 3D graphical modeling program you are refering to is specificaly federaly trademarked as "Lightwave 3D" SN#74071550 which was registered in 1990.
There's also Lightwave.com which is owned by Digital Lightwave, Inc., a NASDAQ registered company who sells components used in optical networking. (Their trademark is under the full name "Digital Lightwave".) I contacted them at one point about them being interested in purchasing the domain but never heard a reply... however, my contact addresses for them were just public whois info so possibly not actually ever read by a human.
I've had various companies in the past contact me about purchasing the domain... game companies and other people interested in setting up an IT related consulting business presumably dealing with optical networking.
The business name and use for me currently is Lightwave Networking (thus lightwave.net (specificaly the .net)) works well for me.
I have no interest in designing and selling a content site... and someone buying the domain would more likely be interested in using it for an optical networking based/IP provider/ISP/etc type company.
My reason for 5 digits is basicaly... any major company who would be presumably interested in the domain... if they could afford $5k.. then adding an extra 0 to that would be a drop in the bucket for them (that's just an example and $50k is not necessarily what i meant by 5 digits.) I realize it's not the dot.com boom anymore... but still I'm not expecting any mom and pop isp to try and pick up the domain.. but someone who's already laid out extreme capital investment in optical networking.
While there's nothing on http://www.lightwave.net/
I can easily show the domain's been used for other things if necessary to fend off a trademark lawsuit on that ground.
Thanks for looking.