I think the issue comes down to trademark infringement no matter how it's being used. They own the name and it is a registered Trademark so legally they are the only ones who can produce anything with the name or logo on it.
Any responsible company no matter how big or small will avoid trademark infringement. These small timers reproducing decal sets and selling them on Ebay will most likely get a letter from Schwinn's attorneys. These are the guys that they are usually after.
If you have a buddy with a plotter and some vinyl and you ask him to make you a set of decals for a restoration project then I doubt you'll hear from them.....unless you blast it all over the Internet.
Legally, you can reproduce things right up until the moment you receive even just a $0.01 for it. Profiting off of something that is trademarked or copywritten is the kicker, and what constitutes "profit" is a little fuzzy at times, but consider this: I can play cover songs all day long without repercussions, but the moment I charge admission to the show, i've crossed the line. Even if I'm not charging the admission, if I'm playing covers for free at a venue but the venue is charging admission, we crossed the line. Even if the venue isn't charging a cover, but they're selling concessions while i play, ASCAP and them can close it down... b/c theoretically, ppl have come to hear the music and bought the Coke b/c it was there, at the show.
But, in the end, I can write "Schwinn" all over whatever bike I want, strap a "McDonald's" headbadge on it, wear my best Elvis impersonator outfit and ride around town playing Britney Spears covers on the ukelele, and I'm in the clear. But, if I take a video of that and put it on youtube, where it could potentially earn ad revenue, then I've infringed...
In the end, the current iteration of Schwinn is stupid to not offer their own repro decals, and they're even stupid to go after ppl for selling bootleg repros, b/c the main thing that sells the current-production "Schwinns" is the buzz created by cool Chicago Schwinns, featured in pics on the Internet or rolling thru neighborhoods, many of which have been restored or modded and include bootleg decals. Take away the nice old Schwinns that many new riders aspire to, and new "Schwinn" sales will suffer.