I have put a lot of work into expanding the character set and making the fonts in a professional quality. I have contacted the original designers and gotten their approval. I offer the fonts for sale at a modest price and with very generous license terms.
If you want to make your own version, you should put in as much work as I did ;)
Note that this restrictions refer to altering the actual fonts themselves, not what you make with them. As long as you don’t alter the font files in font creation software such as FontLab or Fontographer you’re free to create anything you like with them.