The Federal Communications Commission may be moving to let television networks own cable-TV systems, a cross-ownership situation that was banned by the commission in 1970. On Thursday the federal agency revived the issue of lifting the ban on cross-ownership, which it almost did in 1982, by noting that a report by the Commerce Department's national telecommunications information and administration in June recommended the rule be abolished. The agency's three sitting commissioners voted unanimously to seek comment again on the proposal, so the agency can consider eliminating the rule. But Commissioner James H. Quello said he feared that cross-ownership could lead to unfair competition. The FCC also proposed scrapping a rule that limits the term of affiliation agreements between networks and stations to a maximum of two years.