Microsoft has long been one of the most ardent proponents of expanding U.S. copyright law. But that enthusiasm doesn't extend to the new Stop Online Piracy Act, which its lobbyists are quietly working to alter, CNET has learned.

It's little surprise that Web-based companies like Google, Facebook, and Twitter oppose SOPA, which is designed to make allegedly piratical Web sites virtually disappear from the Internet. They, and many civil liberties and human rights groups, worry that SOPA could jeopardize legitimate Web sites too.

BSA

But Redmond's skepticism is notable because unlike the Web companies, Microsoft earns nearly all of its revenue by licensing software--which can, of course, be pirated--and loses money on Bing and its online services division. What's even more telling is that Microsoft had enthusiastically endorsed a narrower version of the copyright bill, called Protect IP, earlier this year.

That concern about SOPA, which is heading toward a committee vote in the House of Representatives next month, led to a rare and embarrassing about-face on the part of the Business Software Alliance, a trade association that represents Microsoft's interests in Washington, D.C. (BSA, along with the Motion Picture Association of America and the Recording Industry Association of America, is among the seven members of the International Intellectual Property Alliance. Among BSA's projects is a pro-copyright Web site for kids featuring Garrett, the copyright-crusading ferret that Wired dubbed one of the "lamest technology mascots ever.")

When Rep. Lamar Smith, a Texas Republican, introduced SOPA last month, BSA distributed a statement saying it "commended" him for it and that the legislation was a "good step...to address the problem of online piracy."

Yesterday, BSA President Robert Holleyman changed his tune, saying in a blog post that SOPA "needs work" and that "valid and important questions have been raised about the bill."

While the wording of SOPA hasn't changed over the last four weeks, the politics have. A person familiar with the situation told CNET that BSA's volte-face came after Microsoft and, to a lesser extent, other members of the trade association had reviewed the bill and informed Holleyman of their displeasure.

Holleyman did not respond to a request for comment today. A spokesman for BSA would say only that "I'm directing you to the blog post."

It's possible that Microsoft is reluctant to oppose SOPA publicly because it would jeopardize its relationship with Smith, the influential chairman of the House Judiciary committee, which oversees copyright law. Microsoft declined to respond to a query from early yesterday, with a representative saying only that we are "unable to accommodate your request."

Microsoft isn't the only company to embrace Protect IP yet have reservations about SOPA. Tim McKone, AT&T's executive vice president of federal relations, told CNET last week that "we have been supportive of the general framework" of Protect IP. But when it comes to SOPA, all AT&T would say is that it is "working constructively with Chairman Smith and others toward a similar end in the House."

One major difference between the two proposals is that SOPA is broader. Protect IP, which is awaiting a Senate floor vote, would allow courts to order AT&T, Comcast, Verizon and other ISPs to pretend that the domain names for targeted Web sites didn't exist. (The Domain Name System, or DNS, translates alphanumeric domain names like CNET.com into the numeric IP addresses actually used by computers, in this case 64.30.224.118.)

SOPA goes further by permitting the Justice Department and courts to order ISPs to block customers from visiting the numeric IP addresses of off-limits Web sites. It also appears to authorize deep packet inspection, which raises privacy concerns.

This week's public position-revision by BSA has inspired some mirth on the part of its customary opponents on copyright law.

Art Brodsky, communications director of Public Knowledge, which previously twitted BSA in a blog post titled "Copyright industry: Copyrights trump human rights?", says he welcomes a potential new ally.

"Generally BSA has been very hawkish on the intellectual property front," Brodsky says. "We're always glad to see them become enlightened on these issues."