I have a question regarding data that has been posted on SRA. what is the best course of action when using a posted dataset and set as public, i do intend to cite the origin of the data, however, do i have to ask for written permission to use the data in any way that would lead to a publication or disseminating results obtained from it through databases?
This question might better be addressed to the relevant staff at NCBI. However, you certainly do not require written permission to use publicly-available data.
The relevant document at NCBI is here; the section Molecular Database Availability reads:
Databases of molecular data on the NCBI Web site include such examples as nucleotide sequences (GenBank), protein sequences, macromolecular structures, molecular variation, gene expression, and mapping data. They are designed to provide and encourage access within the scientific community to sources of current and comprehensive information. Therefore, NCBI itself places no restrictions on the use or distribution of the data contained therein. Nor do we accept data when the submitter has requested restrictions on reuse or redistribution. However, some submitters of the original data (or the country of origin of such data) may claim patent, copyright, or other intellectual property rights in all or a portion of the data (that has been submitted). NCBI is not in a position to assess the validity of such claims and since there is no transfer or rights from submitters to NCBI, NCBI has no rights to transfer to a third party. Therefore, NCBI cannot provide comment or unrestricted permission concerning the use, copying, or distribution of the information contained in the molecular databases.
Data are by default in public domain, however biologists have created a number of policies that specify conditions of reuse. These span from infamous "authorshipware" (you add a person that generate data to list of authors of your paper), to relatively permitive such as "if I published paper on the data, you're free to do whatever you wish". See this question for examples: "Analyze Genome Sequence Not Published". Much of what applies to assembled data, applies to raw reads.
