Over a decade since transparency was introduced as a first-class concept in computing, transparency is still an emerging concept that is quite poorly understood. Also, despite existing research contributions, transparency is yet to be incorporated into the software engineering practice, and the promise it holds remains unfulfilled. Although there is evidence of increasing stakeholders' demand for software and process transparency, the realization of such demand is yet to be fully witnessed within the software engineering practice. There is a need to uncover transparency and how it has so far been conceptualized, operationalized, and challenges faced. We applied a systematic literature review method in search of articles published between January 2006 and March 2022. This study reports a systematic review of the explicit conceptualization and application of transparency in 18 articles out of a total of 162 selected for review. Our study found that transparency remains an under-researched non-functional quality requirement concept, especially as it impacts information and software systems development. Of the 18 articles reviewed, only three studies representing 16.67% conceptualized transparency in software development and focused on the transparency of software artifacts. The remaining 83.33% of studies conceptualized transparency in information systems, focusing on general information and fully functional information systems. Transparency is yet to be fully explored from a theoretical gathering point of view and as a non-functional indicator of software quality hence its slow adoption and incorporation into mainstream software practice. Apart from providing a catalog of transparency factors that stakeholders can use to evaluate transparency achievement, the paper proposed a roadmap to enhance transparency implementation and also provides future research directions.