A two-part curable composition comprises: a Part A component comprising polythiol having a thiol group functionality of at least two, and tertiary amine accelerator; and a Part B component comprising polyene comprising at least two of non-aromatic C—C double bonds, C—C triple bonds, or a combination thereof and organic peroxide curative. At least one of the polythiol or the polyene comprises a respective reaction product of reaction components comprising: HSR1O(CH2CHR2O)aR1SH wherein each R1 independently represents an alkyl group having from 2 to 12 carbon atoms, each R2 independently represents H or CH3, and a represents an integer from 1 to 20; triallyl isocyanurate; H2═CHOR1O(CH2CHR2O)aR1OCH═CH2; and. A method of making a curable composition comprises combining the Part A and Part B components of the two-part curable composition. Methods of sealing a substrate and adhering two substrates, and articles made thereby are also disclosed. (Formula AA)