The sale of Source Telecomputing Company, the McLean home computer company, to the Reader's Digest Association Inc. has been challenged in a new battle in the long feud between the company's chairman, Jack Taub, and William Von Meister, the orginal owner of The Source.

Von Meister yesterday obtained an order from U.S. District Judge Richard Kellam temporarily barring Taub from selling or disposing of any additional shares of Source Telecomputing and forbidding Taub from making use of the sales proceeds without the court's permission.

On Tuesday, Reader's Digest acquired 51 percent of the stock of STC, for a reported $3 million, giving it control of The Source, the home computer information network that has excited considerable acclaim and interest in the telecommunications industry.

Owners of The Source computers are able to receive the United Press International newswire; quotas from stock and commodity exchanges; electronic mail; ready-made programs to perform accounting, word-processing and home finance tasks; restaurant reviews; electronic games and other series at a relatively low cost.

Despite the acclaim for the service, however, it carries a burden of past debts over which Taub and Von Meister have been struggling.

Judge Kellam, district judge for the Eastern District of Virginia, is presiding over a lawsuit between Taub and Von Meister over control of The Source and is awaiting summary arguments from attorneys for both sides.

Von Meister contends that he has a 32 percent interest in Digital Broadcasting Corp., the original company that began marketing The Source.Taub has said he owns 90 percent of Digital Broadcasting, obtaining majority control in 1979 from Von Meister at a time when the company was heavily in debt, Taub says.

Since then, Taub has separated The Source from DBC by setting up STC. "They're two totally separate corporations," he said in an interview. s

That point, however, is disputed by Von Meister. "We have no objection to Reader's Digest investing in The Source provided that the shareholders of DBC have something to say about it," said Michael Nusbaum, Von Meister's attorney. Von Meister, who has personally guaranteed some substantial debts owed by DBC, doesn't want that proceeds from a sale of The Source going to settle Taub's debts first, Nusbaum said.