Uploading content from other users with minor modifications is not allowed under osu!'s
Beatmap Submission Rules without the explicit permission of the original creator(s). Specifically, see point 3:
Do not plagiarise or attempt to steal the work of others. Do not also upload or use other people's work without their explicit permission (including, but not limited to, skins and guest difficulties).
Modifications include, but are not limited to: changing difficulty settings, playback speed, slider velocities, object placement and/or orientation, game mode conversion.
Whether modifications are considered major enough to not fall under the above plagiarism guidelines is at the Global Moderation Team's discretion, so if you have any questions, please contact a team member BEFORE uploading as your content may be removed and a silence issued.
EDIT: Moved to Beatmaps > Help > General Questions subforum.