User blog comment:Warmachine375/When will Gun Gale Online become an anime?/@comment-65.87.40.88-20130813080113/@comment-4631119-20130813080522

Yup, they are both is the 1st Season.

To make two or more arcs constituted as different season, it requires at least one whole season break between the season. Since SAO and ALO are animated in one long run, it's a single multi-season.