I'm now making commercial software for Windows CE O/S, and I want to embed Ubuntu font to my software. The file format will be converted to my own format to speed up my software.
In this case, am I need to obtain some kind of license? Or do it freely with including license.txt files on my software ?
According to the Ubuntu Font Licencing FAQ you can an will be able to use the Ubuntu font for your programs, even if not related directly to Ubuntu as long as you follow the license agreement.
Permission is hereby granted, free of charge, to any person obtaining a copy of the Font Software, to propagate the Font Software, subject to the below conditions:
Each copy of the Font Software must contain the above copyright notice and this licence. These can be included either as stand-alone text files, human-readable headers or in the appropriate machine- readable metadata fields within text or binary files as long as those fields can be easily viewed by the user.
The font name complies with the following:
a) The Original Version must retain its name, unmodified.
b) Modified Versions which are Substantially Changed must be renamed to avoid use of the name of the Original Version or similar names entirely.
(c) Modified Versions which are not Substantially Changed must be renamed to both (i) retain the name of the Original Version and (ii) add additional naming elements to distinguish the Modified Version from the Original Version. The name of such Modified Versions must be the name of the Original Version, with "derivative X" where X represents the name of the new work, appended to that name.The name(s) of the Copyright Holder(s) and any contributor to the Font Software shall not be used to promote, endorse or advertise any Modified Version, except (i) as required by this licence, (ii) to acknowledge the contribution(s) of the Copyright Holder(s) or (iii) with their explicit written permission.
The Font Software, modified or unmodified, in part or in whole, must be distributed entirely under this licence, and must not be distributed under any other licence. The requirement for fonts to remain under this licence does not affect any document created using the Font Software, except any version of the Font Software extracted from a document created using the Font Software may only be distributed under this licence.