2000.10.06 16:35 "RE: PDF is NOT proprietary!", by Ed Grissom
Not (just??) the use of the name, the use of the data structures necessary to R/W the file are copyrighted.
From the PDF spec. (Hopefully a "fair-use" situation)
"The only condition of such copyright permission is that anyone who uses the copyrighted list of data structures and operators in this way must include an appropriate copyright notice. This limited right to use the copyrighted list of data structures and operators does not include the right to copy this book, other copy-righted material from Adobe, or the software in any of Adobe's products that use the Portable Document Format, in whole or in part, nor does it include the right to use any Adobe patents (except as may be permitted by an official Adobe Patent Clarification Notice)."