BOSTON (AP) _ Lotus Development Corp. has won another battle in its aggressive defense of the copyright on its popular Lotus 1-2-3 spreadsheet program.

A federal judge ruled Friday that Borland International Ltd. infringed on certain parts of the Lotus copyright on its 1-2-3 spreadsheet software.

''Lotus 1-2-3 is copyrighted,'' U.S. District Court Judge Robert E. Keeton wrote in a 49-page decision. ''Borland copied copyrightable elements of 1-2-3 that constitute a substantial part of that program. Lotus has sued and Borland is liable.''

Two years ago, Lotus won a copyright infringement case against Paperback Software of Berkeley, Calif. Since then, several small companies have settled out of court with Lotus.

Keeton also ruled, however, that a jury trial is needed to determine how much Borland copied of the so-called ''user interface'' of Lotus 1-2-3. He scheduled a pretrial conference for Sept. 23.

The user interface is a combination of a program's menu commands and command structures and the visual appearance of the software on the computer screen.

''This is a very strong opinion that covers virtually all the bases, and it's a tremendous victory for Lotus and anyone who values meaningful protection of copyrightable software,'' said Lotus attorney Henry Gutman.

''We are disappointed, but not really surprised by this decision,'' said Spencer Leyton, Borland senior vice president of business development. ''As some commentators have said, we think this case will be decided on appeal.''

Keeton said that no matter where Borland got parts of its on-screen menu and menu command structure, it violated the law.

''The fact that Borland used third-party sources as a means of copying the Lotus 1-2-3 menu command hierarchy in no way excuses Borland's deliberate imitation of the Lotus menu structure,'' Keeton wrote.

0838EDT