This thesis primarily aims to identify the current internationalization, localization and quality assurance practices in multilingual open source software. A secondary research objective is to determine the reasons why developers might choose not to localize their (monolingual) software. The data was gathered through a questionnaire targeted at developers of image editing software specifically. There were 61 participants, out of which 32 were developers of localized software and 29 were developers of monolingual software. It was observed that current practices in open source internationalization and localization have not evolved much in recent years and that they still differ significantly from the best practices in this field. Furthermore, quality assurance and planning in particular are usually assigned low priority. Lastly, there seems to be a lack of awareness of localization in the open source community.