TM is an unregistered trademark.
From what I understand, what they lost was their right to claim a "registered" trademark.
TM is not the same as ®.
You can legally slap a TM on anything you use for branding. The ® has more weight in a court of law.
From Wikipedia:
A trademark may be designated by the following symbols:
- ™ (the "trademark symbol", which is the letters "TM", for an unregistered trademark, a mark used to promote or brand goods)
- ℠ (which is the letters "SM" in superscript, for an unregistered service mark, a mark used to promote or brand services)
- ® (the letter "R" surrounded by a circle, for a registered trademark)