Namibia's outspoken newspaper, The Observer, reappeared today after the South African censorship authorities lifted a ban that they had imposed on it three weeks ago.

The Observer is the only newspaper in Namibia that supports the insurgent black nationalist movement, the South-West Africa People's Organization (SWAPO).

It is an unconventional newspaper edited by a white Afrikaner, Johannes Smith.

The censorship authorities, officially titled the Publications and Entertainments Board, banned The Observer Aug. 17 on the ground that its favorable reporting on SWAPO constituted a danger to national security.

Smith appealed to the board to review its own decision during a three-day hearing in Pretoria that ended yesterday.

His lawyer, Bryan O'Linn, argued that although SWAPO was fighting a guerrilla war against South African forces in Namibia, it was also engaged in independence negotiations with the South African government.

He said it was important that the organization's views be made available to the people of Namibia, and The Observer was the only newspaper that did this.

In his judgment, the board's chairman, Kobus Van Rooyen, said SWAPO was partly an insurgent organization and partly a legal political one. He ruled that while some material in The Observer was close to violating national security it had not actually done so.